Pulse generation device



Dec. 8, 1959 L. c. WHITE 2,916,643

PULSE GENERATION DEVICE 2 Sheets-Sheet 1 Filed Dec. 8, 1955 INVENTOR;LORING 0A WHlTE ATTORNEY Dec. 8, 1959 WHlTE 2,916,643

PULSE GENERATION DEVICE 2 Sheets-sheaf. 2

Filed Dec. 8, 1955 Fig. 5

as I BY 7 I I Y I ATTORNEY INVE TOR. LORING C. WHITE This, inventionrelates to vacuum electron discharge United States Patent() devices, andm1ore particularly to discharge tube-s having a pllurality ofdischargegapsjarranged in a magnetic field-and adapted to;produce, output pulsesat an'array oftarget or'collectorelectrodes.v

;-J-From-the following'moredetailed description of the tubesof myinvention. certain similarities of these tubes tqknowmtypes of.so-called switching tubes will be noted. suchrswitching'tubes commonlyhave been employedjin jpnlse coun'tingQ-and pulse distributingapplications-in, which -the electron discharge in a multi-gap tube iscausedto shift from one'gap to a second gap .by application'of a-pulseapplied to a-control or grid electrodeassociated with ;,the target-orcollector electrode 1 ofthe second gap. Thus progression of thedischarges to,;p roduce-pulses in an external circuit or circuits isaccomplished'with the aid of a pattern of input pulses to grid or--control electrodes. Incontrast to these known tubes,-thepulse'generating tubes of my invention are adapted to produce at theoutput a succession of pulses without-the-aid of such input controllingpulses. At-

- tempts also have beemmade to adapt these known typesofacountingjtubestor pulse generation. However, these attempts have beenaccompanied either by the necessity for-.additionalj tube elements,flandresulting complicated circuitry or'byan inherent. inflexibility of suchdevices withrespect to maximum frequencies and ranges ofoperablefrequeneies. t

' ,';-It is therefore an 'object of this invention to provide f a;p.ulsegenerating-tube which is not dependent for frequency control onasupply-of pulsed energy to the tubem :7: .13 further object 'iS tQprovide a pulse, generating tube operable-overawide range offrequencies.

A still furtherobjectis to provide a pulse generating tube having.a'plurality of electron discharge gaps in which transfer of a dischargefrom each gap to an adia cntgap is accomplished rapidly and positivelyby virtue 'ofifiirnovel configuration and arrangement of electrode ntswithin the tube.

he foregoing objects are, realized in tubes of this irwerrtion whichmaybe described generally as-including a-;-heated cathode centrallylocatedzwithin an evacuated envelope, which cathode constitutes acommonelectrode foraplurality of electron discharge gaps. -A generallycircular array ,of anodes is located radially .outward from-the cathode.These anodes serve as collector electrodes or targets, for the dischargegaps. A magnetic field through the evacuated enclosure perpendicular tothe arrayof discharge gaps. is provided by a magnetice tain principlesof operation of known types of counting or switching tubes are alsoinvolved in the present tube. Thus, the interaction of the magneticfield through the discharge gaps and the electrical field established bya potential difference maintained between the cathode and the arrays ofbeam forming and collector electrodes results in the production of anelectron beam within the tube. The beam may be directed into a pathmoving toward any individual collector as a result of changes in theelectric field within the tube. For example, in counter tubes of knowntypes employing this principle of operation, the discharge may bedirected first toward one target or collector electrode andsubsequently, at predetermined intervals, toward other electrodes inan'array by application of voltage pulses from an external sourcesuccessively to the other electrodes. As previously noted in thedescription of the tubes herein described, the applicationiof externallyapplied control pulses is'not employed, and in this respect theparallelism ceases between the principles of operation of the previouslyknowncounter tubes and my novel pulse generating device. Moreparticularly, the changes in the electric field in my tube, essential tothe transfer or stepping of the discharge in rotating fashion about thecathode results from the novel configuration of the beam formingelectrodes and the arrangement of those electrodes relative to thecathode and the target or collector electrodes. As will be obvious frJmthe subsequent more detailed description of these elements of thedevice, each of the beam forming electrodes includes electronintercepting structure extending into the'discharge zone between thecathode and the adjacent target or collector associated with an adjacentbeam forming electrode, this zone being coextensive with the spacewithin the envelope occupied by the electron beam at the time ofdischarge at the gap defined by the cathode and the collector.

In operation, the electron intercepting structure of a particular beamforming electrode picks 'up a'portion of the electrons in the dischargezone of the adjacent gap upon the occurrence of the'beam at that gap.The flow of electrons to the beam forming electrode via the electronintercepting structure is elfective'to cause the potential of the beamforming electrode rapidly'to ap proach that of the cathode.Simultaneously the potentials of the preceding adjacent beam formingelectrode and associated target or collector tend to increase relativeto the cathode by virtue of the extraction of the electrons from theirdischarge gap. .In this way the potential distribution in the electricfield is altered to establish a new path for the electron beam in the'discharge zone between the cathode and target or collector associatedwith the aforementioned particular beam form ing electrode. Once startedin the manner hereinafter set forth, this beam transfer or switchingaction continues sequentially around all the positions defined by thearrays of beam forming and collector electrodes, the action taking placeat a rate determined by the strength of the magnetic field, the spacingof the electrodes, and the external circuitry.

In the drawings:

Fig. 1 is a perspective view of a preferred embodiment of my inventionwith portions of the magnet, surrounding envelope, and supportingstructure removed.

' Fig. 2 is a cross-sectional view of the device of Fig. 1 through 22.

, Fig. 3 is an enlarged plan view of the electrode structure in thedevice of Figs. 1 and 2. v

Fig. 4 is an enlarged plan View of a modified electrode arrangement.

Fig. 5 is a typical circuit employing a sixteen element tube as asixteen output pulse generator.

The preferred embodiment of my invention as disclosed in Figs. 1, 2 and3 comprises a glass envelope 1 having a base 2 wherein conductive leads3 leading from the elements within the envelope are sealed and madeavailable for connecting to the external circuitry through externalterminals as shown. The envelope is evacuated and contains insulatingmica discs 4 and 5 which support and retain in position the electrodesof the device. Centrally located in the glass envelope is a slimrod-like indirectly heated cathode 6 suitably coated with an electronemissive substance. Sixteen target or collector electrodes 722 arearranged in a generally circular array about the cathode. The collectorelectrodes are metal strips of modified L cross-section, one arm beingsubstantially normal to the radius of the tube, and the other armextending generally radially toward the cathode. Sixteen beam forming ortransfer electrodes 3752 are located in the annular space between thecathode and the array of collector electrodes. Each transfer electrodeis arranged in a particular manner with a respective one of thecollector electrodes as hereinafter described.

The beam forming electrodes as shown on an enlarged scale in Fig. 3include an elongated channel-like portion of generally U-shapedcross-section having sides 46a and 46b and a tip or vertex 46c with theopen end overlapping and closely adjacent to the radially directed armof its associated collector electrode and with its closed end or tipfacing toward the cathode. One side or leg of the U-shaped portion iscloser to the radial arm of the collector electrode than is the otherside as best shown in Fig. 3. In the arrangements shown in Figs. 1, 2and 3, a vane 46d consisting of a flat metal plate extends along theside of the beam forming electrode which is more closely adjacent itsassociated collector electrode and toward the center portion of the tubeinto the discharge zone between the cathode and the adjacent target orcollector electrode. This vane may be a separate plate of metal brazedor otherwise conductively secured to the U-shaped portion of theelectrode or alternatively may be an integral part of the U-shapedportion sharply bent to the configuration shown. The distance of the tipor leading edge of the vane from the central axis of the tube is of theorder of three times the diameter of the cathode. Desirably the cathodeshould be of relatively small diameter so that no portion of the beamforming electrode is closer to the surface of the cathode than adistance equivalent to about twice the diameter of the cathode.

The beam forming electrodes and the collector electrodes preferably areconstructed of a non-magnetic nickel alloy. The glass envelope issurrounded by a cylindrical permanent magnet 60 arranged so as toprovide an axial magnetic field which has lines of flux extendingupwardly through the tube as indicated by the conventional symbol inFig. 2.

Under usual operating conditions the beam forming electrodes and thecollector electrodes are biased positive with respect to the cathode.The strength and influence of the electric and magnetic fields are suchthat the electrons move around the cathode, but their path does notextend to the beam forming electrodes, until the potential of one of thebeam forming electrodes is lowered, changing the electric fieldsufficiently to deflect the path of the electron beam outwardly towardthe electrode. As some of the electrons strike the beam formingelectrode a negative resistance action takes place. Current flowing inthe associated circuit of the beam forming electrode causes a potentialdrop to take place across the resistance of the circuit and thus lowersthe potential drop between the beam forming electrode and cathode. Thisaction is cumulative. The lower the potential of the beam formingelectrode becomes the more it distorts the electric field and picks upelectrons, thus causing more and more current to flow in its circuit andcontinually increasing the potential drop across the circuit resistance.As the beam forming electrode approaches cathode potential the entireelectron beam, following lines of equal potential, attempts to flowaround the beam forming electrode.

Due to the action of the electric and magnetic fields the individualelectrons follow a trochoidal path. Some of the electrons strike thebeam forming electrode to provide the negative resistance actionhereinbefore da scribed. The majority of them, however, tend to movealong the vane and then aroundzthe" beam forming electrode, striking thepositively biased collector electrode which is positioned closelyadjacent the beam forming electrode, and thence through the collectorelectrode circuit.

Referring to Fig. 3, and assuming that an electron discharge betweencathode 6 and collector electrode '15 has beenestablished as describedabove, the manner in which the discharge is caused to advance to itsnext position at electrode 16 will be apparent from the followingexplanation. The vane portion- 46d of beam forming electrode 46, whichextends into the discharge zone of collector electrode 15, interceptselectrons from'the discharge-"zone, causing a reduction of the potentialof electrode 46. The flow of electrons through the circuit associatedwith electrode 46 produces the cumulative negative resistance' actionpreviously described, which action continues until the potential ofelectrode 46 isreduced sufficiently to form the discharge with collectorelectrode Has the target. The beam forming electrode 45 returns to itsbiased potential as the electron flow to it and its associated anode 15is reduced to zero. The rate at which this cut-off occurs depends on thetime constant of'the beam forming electrode circuit. The action asdescribed takes place clockwise and sequentially in the array of beamforming electrodes and collector electrodes of the device as indicatedby the arrow in Fig. 2. About of the electron current flow is availableat the collector taking part in the discharge.

Fig. 5 discloses a typicalcircnit employing the device of this inventionto obtain pulses at sixteen outputs. The tube has sixteen sets of beamforming electrodes 37-52 and collector electrodes 7-22 positioned aroundthe oathode 6. The cathode is indirectly heated and is connected througharesistance 23 of about 1500 ohms .to ground. Each collector electrodeis connected through a resistance 24-24 of about 3,300 ohms to thepositive side of a D.C. source 32 of about 200 volts. An outputconnection 31 is provided at each collector electrode. Each beam formingelectrode is connected through a resistance 2525 of about 100,000 ohmstothe positive a side of the D.C. source. A small trimmer capacitor26-26 is placed across each resistance 2525 for adjusting the timeconstant of the beam forming electrode circuit and thus regulating thetime lag between output pulses. Normally closed switches-27 and 28 areprovided for starting and stopping operation of the circuit; Themomentary opening of switch 27 lowers the potential of beam formingelectrode 52 and, as previously described, causes it to distort theelectric field within the tube with resultant electron flow from thecathode to target electrode 22. Opening of the normally closed switch 28reduces the potential on all the beam forming electrodes to near cathodepotential and cuts off electron fiow by eliminating the electric fieldbetween the cathode and other elements ofthe tube. On closing of switch28 so as to return all beam forming electrodes to bias potential noaction occurs because, as previously indicated in this specificatiomtherelative strengths'of the electric and magnetic fields are such as toprevent electrons from reaching the beam forming electrodes. Action canbe reinitiatedonly by opening and then closing the switch 27 asdescribed above. Resistances 29 and 30 are of the order of one megohm.The magnetic field is about 400 gauss.

Devices constructed as hereinabove described, and operating in the abovecircuit have generated pulses at a rate of over one megacycle persecond. The frequency of generated pulses is directly related to thesupply voltage and inversely related to the magnetic field strength andthe time constants of the individual beam forming electrode circuits.

Fig. 4 depicts a modified form of the beam forming electrode which maybe employed in tubes of my invention. The vanes of the channel-like beamforming electrodes in the preferred embodiment hereinbefore describedare eliminated, and the electron intercepting function of the vanes isafforded instead by portions 710! and 72d of the sides 71a, 72a of theU-shaped electrodes 71, 72 farthest away from the respective associatedcollector electrodes 81, 82. This is accomplished, for example, as shownin Fig. 4, in which portion 72d is shown as an extension of one leg 72aof the main portion of the electrode 72, which extension is bent orcurved outwardly at a greater angle with the axis of the U crosssectionthan the angle between the main portion 72a of the side of the U and theaxis thereof so that at least the extreme edge of the extension lieswithin the zone occupied by the path of the electrons moving to targetelectrode 81 from cathode 86. In a manner corresponding to thatdescribed in connection with the vaned electrodes the outwardly bentportion 72d intercepts some of the electrons as they flow to collectorelectrode 81 to induce shifting of the electron flow to electrode 82.

It also has been found possible tooperate the device as a pulsegenerator with other modifications of the electrodes. For example, it ispossible to eliminate the targets and take the outputs from the beamtransfer electrode circuits. However, the greatest amount of usableoutput has been obtained with the preferred embodiment of my inventioninvolving the use of collector electrodes.

With various circuit arrangements a variety of ways of using the tubesof the invention are possible. For example, the number of outputpositions can be reduced by connecting adjacent beam forming electrodesand targets together and properly changing resistance values. Variouscombinations of outputs can be made to obtain different pulse sequenceson difierent output channels. Still further, the time between pulses canbe varied independently by the amount of capacitance and/or resistanceused in the beam forming electrode circuits.

What is claimed is:

1. A pulse generator tube comprising an evacuated envelope enclosing acathode, a plurality of collector electrodes positioned in a circulararray around said cathode, each collector electrode forming an electrondischarge zone with said cathode, a plurality of beam forming electrodesof generally U-shaped cross-section each having its open end disposedtoward one of said collector electrodes and its vertex disposed towardsaid cathode, one beam forming electrode positioned intermediate atleast a portion of each of said collector electrodes and said cathode,each of said beam forming electrodes having an electron interceptingvane extending along one side of said U-shaped cross-section into theelectron discharge zone between an adjacent one of said collectorelectrodes and said cathode, each of said collector electrodes and beamforming electrodes being insulatingly supported from each other and fromsaid cathode and means for producing an axial magnetic field within saidenvelope.

2. A pulse generator tube as in claim 1 in which the said vane of eachbeam forming electrode extends no closer to said cathode than at leasttwice the diameter of said cathode.

3. A magnetron type multiple position beam switching tube comprising anelongated substantially evacuated envelope, an elongated thermioniccathode centrally disposed therein, a plurality of elongated U-shapedbeamforming electrodes symmetrically arranged in a circular array aroundsaid cathode with the open side of the electrode facing outwardly fromthe cathode, a like plurality of elongated substantially L-shaped targetelectrodes symmetrically arranged in a concentric 'circular arrayadjacent to said array of beam-forming electrodes and on the side whichis more remote from said cathode, one section of the L of each targetelectrode extending into the space between the outwardly extendingportions of an adjacent one of said beam-forming electrodes and lyingsubstantially along a radius of said arrays, the extremity of said onesection of the L being closer to one of the outwardly extending portionsof its associated beam-forming electrode than to the other, and theother section of the L of each target electrode extending across thespace between said one outwardly extending portion of a beam-formingelectrode and the other outwardly extending portion of the next adjacentbeam-forming electrode and disposed substantially normal to a radius ofsaid arrays, each of said beam-forming electrodes each further includingan elongated vane extending inwardly toward said cathode along said oneoutwardly extending portion.

4. An electron tube for operation under the influence of crossedmagnetic and electric fields comprising an elongated substantiallyevacuated envelope, a thermionic cathode centrally disposed therein, acircular array of similar U-shaped beam-forming electrodes the sides ofwhich extend away from said cathode, a circular array of similarL-shaped target electrodes disposed adjacent to said array ofbeam-forming electrodes and on the side thereof which is more remotefrom said cathode, one section of the L of each target electrode beingdisposed substantially normal to a radius of the tube and forming abeam-receiving surface and the other section extending into the spacebetween the outwardly extending portions of an adjacent one of saidbeam-forming electrodes and lying substantially along a radius of saidarrays, the extremity of said other section of the L being closer to oneof theoutwardly extending portions of the beamforming electrode than theother, and a further structural member conductively joined to the saidone outwardly extending portion of each of said beam-forming electrodesand extending into the electron discharge zone between an adjacent oneof said target electrodes and said cathode.

5. Apparatus in accordance with claim 4 wherein the further structuralmember is an elongated vane extending inwardly toward said cathode alongsaid one outwardly extending portion of the beam-forming electrode.

6. Apparatus in accordance with claim 5 in which the said vane extendsno closer to said cathode than at least twice the diameter of saidcathode.

7. Apparatus in accordance with claim 4 wherein the further structuralmember is an extension of said other outwardly extending portion of thebeam-forming electrode, said extension being bent outwardly of the planeof said other portion such that at least a portion thereof lies withinthe path of electrons moving from said cathode to the target electrode.

References Cited in the file of this patent UNITED STATES PATENTS andControls, Tele-Tech, vol. 12, No. 9, September 1953, pages 88-90, 108,-112, 114.

